In recent years, in wireless communication systems, a MIMO communication technology has been proposed as technology for achieving an increase in transmission speeds, an increase in communication capacities, an improvement in reception qualities, and so on. In the MIMO communication technology, a transmitter having multiple antennas and a receiver having multiple antennas are used. Independent data streams are transmitted from the antennas of the transmitter and are received by the antennas of the receiver. On the basis of the received signals, the receiver separates the transmission signals (the data streams) that are mixed on propagation channels, by using channel matrices representing the state (environment) of communication channels.
In the wireless communication system, as the number of antennas increases, a greater number of signals are transmitted and received for processing. Thus, for example, the cost, size, and power consumption of circuitry coupled to the antennas increase and the complexity of the entire system also increases. Thus, in order to reduce the cost, the complexity, and so on, a technology for selecting a combination of antennas used from all the antennas has been proposed (refer to, for example, Japanese Unexamined Patent Application Publication No. 2007-13547).
During selection of the antenna combination, the wireless communication system selects an appropriate antenna combination that allows high-level communication performance (e.g., a high-level communication capacity and a diversity gain) to be maintained. However, a selection criterion for selecting an appropriate antenna combination is highly complicated in general. In addition, as the number of antennas provided increases, the number of antenna combinations also increases. Thus, processing for selecting an appropriate antenna combination from all combinations becomes complicated and a large amount of processing time is required.